Immunoglobulin (Ig) light chain restriction (LCR) detection is an important molecular diagnostic tool in the differential diagnosis that includes lymphoid hyperplasia, atypical lymphoid hyperplasia, chronic inflammation, and B cell neoplasms. LCR can be detected by flow cytometry (FCM) as an abnormal kappa:lambda ratio on the cell surface. However, FCM requires fresh (unfixed) tissue. Some B cell lymphomas lack surface Ig expression detectable by FCM, some demonstrate nonspecific antibody binding. Often only formalin-fixed paraffin-embedded (FFPE) tissue is available for pathologic evaluation. Current methods of LCR identification in FFPE tissue include immunohistochemistry (IHC) and conventional chromogenic in situ hybridization (CISH), which measure kappa or lambda protein and mRNA, respectively. However, both IHC and conventional CISH lack sufficient sensitivity to detect LCR in many non-Hodgkin lymphoma (NHL), including the most common NHL variants - follicular lymphoma, diffuse large B cell lymphoma, small B lymphocytic lymphoma, and extranodal marginal zone lymphoma of MALT type. RNAscope is a novel RNA in situ hybridization technology which has single-molecule detection sensitivity and is fully compatible with FFPE tissue using either chromogenic or fluorescent detection. We have developed a manual bright-field kappa and lambda duplex RNA ISH assay for LCR, which has demonstrated broad applicability to all NHL subtypes. In this project, we will develop a fully automated duplex RNAscope LCR assay with digital pathology interpretation, which should greatly facilitate clinical adoption of this novel assay.